Compositions and methods for immunotherapy

ABSTRACT

The present invention provides compositions and methods for immunotherapy, which include shelf-stable pharmaceutical compositions for inducing antigen-specific T cells. Such compositions are employed as components of an artificial antigen presenting cell (aAPC), to provide a patient with complexes for presentation of an antigen (e.g., a tumor antigen) and/or a T cell co-stimulatory molecule.

PRIORITY

This Application claims the benefit of, and priority to, U.S.Provisional Application No. 61/838,547, filed Jun. 24, 2013, and U.S.Provisional Application No. 61/948,916, filed Mar. 6, 2014, which arehereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to compositions, including pharmaceuticalcompositions, and methods that are useful for immunotherapy.

BACKGROUND

An antigen-presenting cell (APC) is a cell that processes and displaysantigenic peptides in complexes with major histocompatibility complex(MHC) proteins on their surfaces. Effector cells, such as T-cells, mayrecognize these peptide-MHC (pMHC) complexes using receptors, such asT-cell receptors (TCRs).

Dendritic cells (DCs) are an example of an antigen presenting cell thatcan be stimulated to effectively present antigen and support expansionof immune effect cells, thereby activating a cytotoxic response towardsan antigen. In some immunotherapies, DCs are harvested from a patientand either pulsed with an antigen or transfected with a viral vector.Upon transfusion back into the patient these activated cells presenttumor antigen to effector lymphocytes (e.g. CD4⁺ T cells, CD8⁺ T cells,and B cells). If properly executed this therapy can initiate a cytotoxicresponse against cells expressing antigens (including tumor antigens).

However, DC immunotherapy, like many immunotherapies faces significantlimitations. For example, there is a discrepancy between strong andantigen-specific T cell responses in vaccinated cancer patientsdetectable ex vivo and only weak clinical responses. Janikashvili N etal., Personalized dendritic cell-based tumor immunotherapy.Immunotherapy 2010 Jan. 1; 2(1):57.

There remains a need for compositions (including shelf-stablepharmaceutical compositions) and methods that are effective forimmunotherapy, including antigen-specific immunotherapy.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides compositions and methods forimmunotherapy, which include shelf-stable pharmaceutical compositionsfor inducing antigen-specific T cells in a patient. Such compositionsare useful for the treatment of, for example, cancer and infectiousdisease. The composition in some aspects is an artificial antigenpresenting cell (aAPC), which comprises a pharmaceutically acceptablebead or particle having antigen presenting complexes and optionally Tcell co-stimulatory signals on its surface, to provide a patient withmolecular complexes that present one or more antigens (e.g., tumorantigen(s)) in the proper context for activation of antigen-specific Tcells. The bead or particles are designed to provide pharmacodynamicadvantages, including circulating properties, biodistribution, anddegradation kinetics, as well as activity. Such parameters include size,surface charge, polymer composition, ligand conjugation chemistry,ligand density, among others.

In some embodiments, the T-cell co-stimulatory signal is an anti-CD28antibody or portion thereof, which may comprise human heavy chain aminoacid sequences, including sequences selected from IgG, IgD, IgA, or IgMisotypes. In some embodiments, the immunoglobulin sequences includehuman IgG constant and variable sequences. The framework (FW) sequencesmay be modified to contain important or desired murine frameworkresidues to maintain the integrity of the antigen-binding site(s). Thecomplementarity determining regions (CDRs) may be based on a murineantibody amino acid sequence (e.g., 9.3 mAb), or other CD28 bindingsequence of which many are known. In some embodiments, the antibodyheavy chain is a variant of a human IGHV4 (e.g., IGHV4-59) germline FW.In some embodiments, the antibody comprises a light chain and the lightchain is a variant of a human IGKV4-01 FW. The antibody may comprise aconstant region and the constant region may be human IgG4 or variantthereof.

The co-stimulatory molecule may be conjugated to a solid support withantigen-presenting molecular complexes, to induce antigen-specific Tcells. The antigen-presenting molecular complex may include MHC Class Iand/or Class II complexes, or portions thereof comprising anantigen-binding cleft. In some embodiments, the molecular complexcomprises one or more HLA amino acid sequences (e.g., comprises theextracellular domain of HLA or antigen-presenting portion thereof),which may contain additional sequences, such as immunoglobulinsequences, or other dimerizing or stabilizing sequence. HLA-Igdimerizing fusions in some embodiments provide advantages in stabilityand/or binding affinity.

Thus, in some embodiments, the invention provides a bead- orparticle-conjugated molecular complex for presentation of antigen to Tcells, where the complex comprises an amino acid sequence forming aClass I or Class II antigen binding cleft, or portion thereof. The aminoacid sequences of the antigen presenting complex may include fusions toheterologous sequences, to provide stability, affinity, and stericadvantages, for example. In some embodiments, the heterologous sequencesinclude immunoglobulin sequences. In some embodiments, the molecularcomplex includes HLA (e.g., HLA-A2) amino acid sequences fused toheterologous sequences, such as immunoglobulin sequences. In someembodiments, the immunoglobulin comprises a human heavy chainimmunoglobulin sequence (e.g., IGVH4), which can include immunoglobulinconstant sequences to provide dimeric HLA, and may optionally comprisevariable region sequences. The variable sequences if present can beoptionally modified to reduce or eliminate potential antigen binding,and optionally with no murine FW residues. The HLA amino acid sequencemay be HLA-A*02:01 (IMGT Accession No. HLA00005) or a derivativethereof.

The T cell co-stimulatory ligand and/or antigen presenting complexes (aswell as other ligands disclosed herein, including targeting ligands) maybe conjugated to a solid support for ex vivo or in vivo antigenpresentation and antigen-specific T cell activation. In someembodiments, the solid support is a bead or particle (e.g., PLGA orPLGA-PEG particle) with surface functional groups for coupling ligands.The particles are designed to provide pharmacodynamic advantages,including circulating properties, biodistribution, and degradationkinetics, as well as activity. Such parameters include size, surfacecharge, polymer composition, ligand conjugation chemistry, liganddensity, among others.

The pharmaceutical composition in the various embodiments may furthercomprise an antigenic peptide for presentation to T cells, and which maybe co-formulated with the ligand-conjugated bead or particle. In variousembodiments, the pharmaceutical composition is shelf stable, and may beprovided in lyophilized form for reconstitution prior to administration,or alternatively provided in another convenient format foradministration to patients (e.g., by parenteral administration).

The pharmaceutical compositions described herein are useful forimmunotherapy, for example, in methods for inducing the formation ofantigen-specific cytotoxic T cells, by administering an effective amountof the composition to a patient in need. In particular, antigenpresenting platforms can be useful for treating patients with infectiousdiseases, cancer, or autoimmune diseases, or to provide prophylacticprotection to immunosuppressed patients.

The invention further provides polynucleotides encoding the amino acidsequences described herein, as well as host cells expressing the same.

This invention is further illustrated by the following non-limitingexamples.

The details of the invention are set forth in the accompanyingdescription and claims below. Although methods and materials similar orequivalent to those described herein can be used in the practice ortesting of the present invention, illustrative methods and materials arenow described. Other features, objects, and advantages of the inventionwill be apparent from the description and from the claims. In thespecification and the appended claims, the singular forms also includethe plural unless the context clearly dictates otherwise. Unless definedotherwise, all technical and scientific terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 show three humanized variable heavy sequences for anti-CD28.

FIGS. 4-6 show three humanized variable light sequences for anti-CD28.

FIG. 7 shows a modified constant heavy sequence.

FIG. 8 shows a constant κ Light sequence.

FIG. 9 shows a humanized non-CD28-binding variable region forconstructing an HLA fusion.

FIG. 10 shows the amino acid sequence for humanized HLA-IgG4HC.

FIG. 11 shows the amino acid sequence for Light Chain 3 (LC3, or Vκ3).

FIG. 12 shows the amino acid sequence for Heavy Chain 1 (HC1).

FIG. 13 shows the amino acid sequence for Heavy Chain 2 (HC2).

FIGS. 14-16 show expression constructs for expression in STABLEFAST-NS0Cell Line.

FIG. 17 shows that the humanized anti-CD28 mAb is not a super-agonist.

FIG. 18 shows that the humanized anti-CD28 clones specifically stainCD28 on a human T-cell line. FIG. 18(A): staining with murine anti-humanCD8 mAb (clone 9.3, Isotype IgG2a); FIG. 18(B): staining with humanizedanti-CD28 (isotype IgG4).

DETAILED DESCRIPTION OF THE INVENTION

The following abbreviations are used throughout: BLAST—Basic LocalAlignment Search Tool, CDR—Complementarity determining region, Cκ—Kappalight chain constant region, Fc—Antibody fragment crystallisable region,Fw—Framework region (of variable regions), HLA—Human leukocyte antigen,MHC—Major histocompatibility complex, VH—Variable heavy, Vκ—Variablekappa light, and V region—Variable region of an antibody, either VH orVκ.

The present invention provides compositions and methods forimmunotherapy, which include shelf-stable pharmaceutical compositionsfor inducing antigen-specific T cells in a patient. In some embodiments,the compositions comprise dimeric HLA antigen presenting complexes. Insome embodiments, the compositions comprise humanized immunoglobulinsequences or portions thereof, which may be employed as components ofthe ligands on artificial antigen presenting cells (aAPCs), to provide apatient with dimeric molecular complexes for presentation of one or moreantigens (e.g., tumor antigen(s)) and optionally one or moreco-stimulatory signals. Antigen presenting platforms, as described inmore detail below, can be based on artificial solid supports, such aspharmaceutically acceptable supports including latex or polymeric beadsor particles.

In some embodiments, the T-cell co-stimulatory signal is an anti-CD28antibody or portion thereof. In some embodiments, the anti-CD28 antibodycomprises sequences of at least one human immunoglobulin isotypeselected from IgG1, IgG2, IgG3, IgG4, IgD, IgA, or IgM. For example, theanti-CD28 antibody may be an IgG isotype, and may contain sequences ofone or more IgG germline framework sequences. For example, the anti-CD28may contain a human IGHV4 heavy chain amino acid sequence, which may bemodified with from one to fifteen amino acid modifications. Themodifications may comprise murine framework residues to support theintegrity of the antigen binding site(s).

The complementarity determining region (CDR) in some embodiments isbased on a murine antibody amino acid sequence, which may optionallyhave from one to ten, such as from one to five, amino acidmodifications. In some embodiments, one, two, three, or more CDRs arebased on mouse 9.3 mAb (Tan et al., J. Exp. Med. 1993 177:165), which ispublicly available. Exemplary CDRs are shown in FIGS. 1-6. In someembodiments, the antibody has the full set of heavy chain and/or fullset of light chain CDRs of 9.3 mAb. For example, in some embodiments theheavy chain variable region contains one, two or three of the followingCDRs, which optionally may each be modified by one, two, or three aminoacid substitutions, deletions, or additions: CDR1 (DYGVH), CDR2(VIWAGGGTNYNSALMS), and CDR3 (DKGYSYYYSMDY). In some embodiments, thelight chain variable region contains one, two, or three of the followingCDRs, which each may be modified by one, two, or three amino acidsubstitutions, deletions, or additions: CDR1 (RASESVEYYVTSLMQ), CDR2(AASNVES), and CDR3 (QQSRKVPYT).

Alternative CDR sequences, variable regions, or CD28-binding ligands maybe employed in various embodiments. Alternative ligands and antibodiesare described in U.S. Pat. No. 7,612,170, U.S. Pat. No. 6,987,171, andU.S. Pat. No. 6,887,466, for example, and these disclosures are herebyincorporated by reference in their entireties.

In some embodiments, the antibody heavy chain comprises a variant of ahuman IGHV4-59 germline framework (FW), which is modified to includefrom 5 to 15 murine FW residues. In some embodiments, the antibodycomprises light chain amino acid sequences, and the light chainsequences may be a variant of human IGKV4-01 FW sequences, and which maybe modified to include from 3 to 15 murine FW residues.

The anti-CD28 human heavy chain sequence may be modified, for example,to comprise one or more (e.g., 2 or more, 3 or more, 4 or more, 5 ormore, or all) murine Fw residues at positions 1, 3, 6, 37, 48, 67, 71,73, 76, 78, 82, 82a, and 82c (based on Kabat numbering). The murine Fwresidues at these positions can be as in 9.3 mAb. The light chain may bemodified to comprise one or more (e.g., 2 or more, 3 or more, 4 or more,5 or more, or all) murine Fw residues at positions 3, 4, 49, 70, 85, 87,and 80. Selected murine Fw residues may support the integrity of theantigen-binding sites. The humanized anti-CD28 antibody maintains theaffinity for CD28 and T cell co-stimulatory activity of 9.3 mAb, and isat least 40%, 50%, 75%, 80%, 90%, and in some embodiments 100% or moreeffective for CD28 binding than 9.3 mAb. In various embodiments, theanti-CD28 mAb is not a super agonist.

The antibody may comprise a constant region and the constant region maybe any isotype. In some embodiments, the antibody constant region ishuman IgG4 or variant thereof. In some embodiments, the constant regioncomprises one or more hinge stabilizing mutations, which may beintroduced in the CH chain (e.g., S241, which may be substituted withP). In some embodiments, the antibody comprises a constant region andthe constant region comprises one or more mutations suitable forchemically coupling the antibody to a solid support. The one or moremutations suitable for coupling may create an amino acid side chainfunctional group (e.g., thiol, amine, or hydroxyl), such as an unpairedcysteine (e.g., at S473). Other changes to the constant region includethose modifications to reduce Fc gamma receptor binding. For example,the CH chain may be modified at L248, e.g., L248E.

In some embodiments, the antibody is an antibody fragment, such asF(ab′)₂ or Fab, or is a single chain antibody, or other antigen-bindingantibody fragment. For example, the antibody fragment can be a singlechain variable fragment of the humanized mAb described herein or otheranti-CD28.

In some embodiments, the co-stimulatory molecule is a single chainvariable fragment (scFv) comprising or consisting essentially of theantigen binding loops formed by the VH and VL chains of an antiCD28 mAb,such as an antibody described herein, scFv antibody constructs maycomprise one or several (2, 3, 4, or 5) VH and VL hypervariable regionchains (the portion of each chain that together form the 3-D antigenicepitope binding pockets) linked together in head-head or head-tailconfigurations by short peptide linkers. Such constructs can beconveniently produced via a completely synthetic route due to theirsmaller size. Further, scFv can exhibit lower potential forimmunogenicity.

In other embodiments, the co-stimulatory ligand is a bi-specificconstruct comprising one or more HLA molecules joined to a scFv of aco-stimulatory molecule ligand or inhibitory ligand. The antigenpresenting complex and co-stimulatory or inhibitory ligand may beconjugated through a peptide tether that allows the bi-specificconstruct to be covalently linked to a nanoparticle surface. In someembodiments, such constructs produce the same activity as nanoparticlescontaining larger constructs of HLA and co-stimulatory or inhibitoryligands each linked to the NP surface independently, thereby providingmanufacturing advantages.

The co-stimulatory molecule may be conjugated to a solid support withantigen-presenting molecular complexes, to induce antigen-specific Tcells. The antigen-presenting molecular complex may include MHC Class Iand/or Class II complexes, or portions thereof comprising anantigen-binding cleft. In some embodiments, the molecular complexcomprises one or two HLA amino acid sequences, which may containadditional heterologous sequences, such as immunoglobulin sequences.Alternative heterologous sequences include dimerizing amino acidsequences such as c-fos and c-jun. HLA-fusions in some embodimentsprovide additional advantages in stability and/or binding affinity.

In various embodiments, the antigen presenting complex is either an MHCclass I molecular complex or an MHC class II molecular complex, oralternatively CD1d. The MHC class I molecular complex may comprise atleast two fusion proteins. A first fusion protein comprises a first MHCclass I α chain and a first immunoglobulin heavy chain and a secondfusion protein comprises a second MHC class I α chain and a secondimmunoglobulin heavy chain. The first and second immunoglobulin heavychains associate to form the MHC class I molecular complex. The MHCclass I molecular complex comprises a first MHC class I peptide bindingcleft and a second MHC class I peptide binding cleft. The MHC class IImolecular complex can comprise at least four fusion proteins. Two firstfusion proteins comprise (i) an immunoglobulin heavy chain and (ii) anextracellular domain of an MHC class IIβ chain. Two second fusionproteins comprise (i) an immunoglobulin light chain and (ii) anextracellular domain of an MHC class IIα chain. The two first and thetwo second fusion proteins associate to form the MHC class II molecularcomplex. The extracellular domain of the MHC class IIβ chain of eachfirst fusion protein and the extracellular domain of the MHC class IIαchain of each second fusion protein form an MHC class II peptide bindingcleft. Antigenic peptides are bound to the peptide binding clefts. Invarious embodiments, the immunoglobulin sequence is a partial heavychain sequence comprising the hinge region to support dimerization.

In some embodiments, the antigen presenting complex is a synthetic orrecombinant HLA monomer engineered to contain an unpaired cysteine, orusing a naturally occurring unpaired cysteine, for conjugation tonanoparticles. Further, the co-stimulatory signal (or otherantibody-based ligand) may be a Fab or scFv. In such embodiments, thetwo signals may be combined in a single multi-functional constructcomprising an HLA molecule tethered to an antigen binding antibodyfragment (e.g., scFv) that binds to a desired receptor.

In other aspects and embodiments, the invention provides a bead- orparticle-conjugated molecular complex for presentation of antigen to Tcells, where the complex comprises a humanized immunoglobulin sequenceor portion thereof fused to an antigen presenting sequence, e.g., an HLAamino acid sequence. In some embodiments, the immunoglobulin sequence isa human heavy chain sequence (e.g., IGHV4 framework). The variableregion does not comprise an antigen binding activity to CD28, or otherhuman protein. The HLA amino acid sequence may be HLA-A*02:01 (IMGTAccession No. HLA00005) or a derivative or fragment thereof, such as aderivative having from 1 to 10, or from 1 to 5, amino acidsubstitutions, deletions, or insertions. The humanized immunoglobulinsequence may further comprise a linker amino acid sequence between theHLA and immunoglobulin sequences. Preferably, the linker lacksimmunogenicity. The molecular complex may further comprise β2microglobulin peptide.

In various embodiments, the immunoglobulin fusion sequences is of IgG,IgD, IgA, or IgM isotype, and may be derived from any human germlineframework. The germline framework includes IGHV4 (e.g., IGHV4-59), whichmay or may not contain one or more of the murine framework residuesdescribed with respect to anti-CD28. In some embodiments, the heavychain of the anti-CD28 antibody described above (with or without murineframework residues) is fused to HLA in accordance with this aspect, andin such embodiments, the variable region is modified to reduce oreliminate CD28 binding.

In some embodiments, the HLA fusion construct contains no variable chainsequences. For example, the HLA or antigen presenting complex can befused to an Ig constant region sequence above the hinge region toprovide a dimeric HLA. For example, an HLA or antigen presenting portionthereof may be conjugated to a CH1 portion of each IgG heavy chain. AllIgG molecules consist of two identical heavy chains (constant andvariable regions) joined together by disulfide bonds in the hinge region(upper and lower). For example, in some embodiments, an HLA molecule orantigen presenting complex is fused to the CH1 (N-terminal end of theIgH chain above the hinge region), thereby creating a dimeric fusionprotein that is smaller due to lack of any VH and VL light chainsequences. Such a construct may provide manufacturing advantages, aswell as exhibit less potential for immunogenicity.

In still other embodiments, the antigen presenting complexes (e.g., HLAsequences) do not contain Ig fusion partners, and are monomeric. Forexample, in some embodiments, the C-terminal end of the antigenpresenting complex or HLA molecule (e.g. HLA-A2, etc.) contains apeptide tether sequence suitable for site-directed binding to afunctional group (e.g. a maleimide moiety) on a solid/semi-solidsubstrate such as a synthetic nanoparticle (e.g. PLGA-PEG-maleimideblock polymers, or other particles described herein). The tethersequence may contain any suitable sequence, which may be predominatelycomposed of hydrophilic residues such as Gly, Ser, Ala, and Thr, such astwo, three, four, or five repeats of GGGSG or AAAGG, with cysteineresidue incorporated somewhere within the about 5 to about 15 (or about5 to about 10 amino acid) tether. The cysteine residue should beincorporated at a site predicted not to form intramolecular disulfidebonds.

In some embodiments, the HLA-Ig fusion or other HLA construct furthercomprises an antigenic peptide bound to the HLA for presentation to Tcells. The antigenic peptide can comprise an antigenic portion of one ormore of tyrosinase, hTERT, MAGE-1, MAGE-3, gp-100, NY-ESO-1, MelanA/Mart-1, HPV 16-E7, gp75/brown, BAGE, and S-100 and/or any of theantigenic peptides as described in WO 2004/006951 for presentation byClass I or Class II complexes, the contents of which are herebyincorporated by reference in their entirety. The HLA complexes may beattached to a solid support, such as a bead or particle as described,for presentation of antigen to T-cells optionally with co-stimulatorysignal.

Other signals that can be provided with the antigen presenting complexinclude: CD80 (B7-1), CD86 (B7-2), B7-H3, 4-1BBL, CD27, CD30, CD134(OX-40L), B7h (B7RP-1), CD40, LIGHT, (or Ig fusions, optionallyhumanized as described herein, of the such molecules or active portionsthereof), antibodies that specifically bind to HVEM, antibodies thatspecifically bind to CD40L, antibodies that specifically bind to OX40,antibodies that specifically bind Fas, antibodies that specifically bindPD1, antibodies that specifically bind to GITR, and antibodies thatspecifically bind to 4-1BB.

Adhesion molecules useful for antigen presenting platforms of theinvention may mediate the adhesion of the platform to a T cell or to a Tcell precursor. Adhesion molecules useful in the present inventioninclude, for example, ICAM-1 and LFA-3.

T cell growth factors affect proliferation and/or differentiation of Tcells. Examples of T cell growth factors include cytokines (e.g.,interleukins, interferons) and superantigens. Particularly usefulcytokines include IL-2, IL-4, IL-7, IL-10, IL-12, IL-15, and gammainterferon. T cell growth factors may be encapsulated in the beads orparticles or chemically conjugated or adsorbed to the surface. Thus, insome embodiments, the nanoparticles further comprise a therapeuticcompound or protein/peptide entrapped in the hydrophobic core of theparticle (e.g. a chemotherapy agent, cytokine or interleukin such asIL-2, a chemokine like CCL9 that attracts T cells, and/or a checkpointinhibitor molecule like anti-PD1 antibody or anti-PD1 peptide). Such anaAPC in some embodiments is constructed to target specific cells forstimulation or inhibition as well as reprogramming. In some embodiments,entrapped compounds are released by degradation of the particle matrix.Such an aAPC could make combination therapies more tolerable andefficacious by limiting unwanted activity due to off-targetinteractions.

Antigens presented in accordance with aspects of the invention includetumor associated antigens. Tumor-associated antigens include uniquetumor antigens expressed exclusively by the tumor from which they arederived, shared tumor antigens expressed in many tumors but not innormal adult tissues (oncofetal antigens, cancer/testis antigens), andtissue-specific antigens expressed also by the normal tissue from whichthe tumor arose. Tumor-associated antigens can be, for example,embryonic antigens, antigens with abnormal post-translationalmodifications, differentiation antigens, products of mutated oncogenesor tumor suppressors, fusion proteins, or oncoviral proteins. A varietyof tumor-associated antigens are known in the art, and many of these arecommercially available. Oncofetal and embryonic antigens includecarcinoembryonic antigen and alpha-fetoprotein (usually only highlyexpressed in developing embryos but frequently highly expressed bytumors of the liver and colon, respectively), placental alkalinephosphatase sialyl-Lewis X (expressed in adenocarcinoma), CA-125 andCA-19 (expressed in gastrointestinal, hepatic, and gynecologicaltumors), TAG-72 (expressed in colorectal rumors), epithelialglycoprotein 2 (expressed in many carcinomas), pancreatic oncofetalantigen, 5T4 (expressed in gastric carcinoma), alpha fetoproteinreceptor (expressed in multiple tumor types, particularly mammarytumors), and M2A (expressed in germ cell neoplasia).

In some embodiments, at least one antigen is a Cancer/Testis (CT)antigen, which may include NY-ESO-1, MAGE-A. B, and C, CTAG-1, CTAG-45,GAGE, and SSX, which are normally expressed by germ cells of the testisand not in normal adult somatic tissues. However, numerous types ofcancer cells have been shown to express CT antigens including melanoma,breast, liver, lung, ovary, and Hodgkin Lymphoma.

Tumor-associated differentiation antigens include tyrosinase (expressedin melanoma) and particular surface immunoglobulins (expressed inlymphomas).

Mutated oncogene or tumor-suppressor gene products include Ras and p53,both of which are expressed in many tumor types, Her-2/neu (expressed inbreast—and gynecological cancers), EGF-R, estrogen receptor,progesterone receptor, retinoblastoma gene product, myc (associated withlung cancer), ras, p53 nonmutant associated with breast tumors, MAGE-1,and MAGE-3 (associated with melanoma, lung, and other cancers).

Other tumor antigens include fusion proteins such as BCR-ABL, which isexpressed in chromic myeloid leukemia, and oncoviral proteins such asHPV type 16, E6, and E7, which are found in cervical carcinoma.Tissue-specific tumor antigens include melanotransferrin and MUC1(expressed in pancreatic and breast cancers); CD 10 (previously known ascommon acute lymphoblastic leukemia antigen, or CALLA) or surfaceimmunoglobulin (expressed in B cell leukemias and lymphomas); the αchain of the IL-2 receptor, T cell receptor, CD45R, CD4+/CD8+(expressedin T cell leukemias and lymphomas); prostate-specific antigen andprostatic acid-phosphatase (expressed in prostate carcinoma); gp100,MelanA/Mart-1, tyrosinase, gp75/brown, BAGE, and S-100 (expressed inmelanoma); cytokeratins (expressed in various carcinomas); and CD19,CD20, and CD37 (expressed in lymphoma).

In some embodiments, the antigenic peptides include MART-1, gp100,NY-ESO-1, and MAGE-A3 which are presented by the HLA antigen presentingcomplexes described herein, such as the HLA-Ig fusion complex describedherein.

In still other embodiments, the composition comprises a cocktail of aplurality of antigens of the tumor type, such as at least 2, 3, 4, 5, 6,7, 8, 9, or 10 antigens (e.g., from 2 to 10 or from 3-8 antigens).

In some embodiments, the antigen is an autoantigen, which is anorganism's own “self antigen” to which the organism produces an immuneresponse. Autoantigens are involved in autoimmune diseases such asGoodpasture's syndrome, multiple sclerosis, Graves' disease, myastheniagravis, systemic lupus erythematosus, insulin-dependent diabetesmellitis, rheumatoid arthritis, pemphigus vulgaris, Addison's disease,dermatitis herpetiformis, celiac disease, and Hashimoto's thyroiditis.For example, diabetes-related autoantigens include insulin, glutamicacid decarboxylase (GAD) and other islet cell autoantigens, e.g., ICA512/IA-2 protein tyrosine phosphatase, ICA12, ICA69, preproinsulin or animmunologically active fragment thereof (e.g., insulin B-chain, A chain,C peptide or an immunologically active fragment thereof), IGRP, HSP60,carboxypeptidase H1, peripherin, gangliosides (e.g., GM1-2, GM3) orimmunologically active fragments thereof.

In some embodiments, the antigen(s) are of infectious agents, such ascomponents of protozoa, bacteria, fungi (both unicellular andmulticellular), viruses, prions, intracellular parasites, helminths, andother infectious agents that can induce an immune response. Bacterialantigens include antigens of gram-positive cocci, gram positive bacilli,gram-negative bacteria, anaerobic bacteria, such as organisms of thefamilies Actinomycetaceae, Bacillaceae, Bartonellaceae, Bordetellae,Captophagaceae, Corynebacteriaceae, Enterobacteriaceae, Legionellacene,Micrococcaceae, Mycobacteriaceae, Nocardiaceae, Pasteurellaceae,Pseudomonadaceae, Spirochaetaceae, Vibrionaceae and organisms of thegenera Acinetobacter, Brucella, Campylobacter, Ervsipelothrix,Ewingella, Francisella, Gardnereïla, Helicobacter, Levinea, Listeria,Streptobacillus and Tropheryma. Antigens of protozoan infectious agentsinclude antigens of malarial plasmodia, Leishmania species, Trypanosomaspecies and Schistosoma species. Fungal antigens include antigens ofAspergillus, Blastomyces, Candida, Coccidioides, Cryptococcus,Histoplasma, Paracoccicioides, Sporothrix, organisms of the orderMucorales, organisms inducing choromycosis and mycetoma and organisms ofthe genera Trichophyton, Microsporum, Epidermophyton, and Malassezia.Antigens of prions include the sialoglycoprotein PrP 27-30 of the prionsthat cause scrapie, bovine spongiform encephalopathies (BSE), felinespongiform encephalopathies, kuru, Creutzfeldt-Jakob Disease (CJD),Gerstmann-Strassler-Scheinker Disease (GSS), and fatal familial insomnia(FFI). Intracellular parasites from which antigenic peptides can beobtained include, but are not limited to, Chlamydiaceae,Mycoplasmataceae, Acholeplasmataceae, Rickettsiae, and organisms of thegenera Coxiella and Ehrlichia. Viral peptide antigens include, but arenot limited to, those of adenovirus, herpes simplex virus, papillomavirus, respiratory syncytial virus, poxviruses, HIV, influenza viruses,and CMV. Particularly useful viral peptide antigens include HIV proteinssuch as HIV gag proteins (including, but not limited to, membraneanchoring (MA) protein, core capsid (CA) protein and nucleocapsid (NC)protein), HJV polymerase, influenza virus matrix (M) protein andinfluenza virus nucleocapsid (NP) protein, hepatitis B surface antigen(HBsAg), hepatitis B core protein (HBcAg), hepatitis e protein (HBeAg),hepatitis B DNA polymerase, hepatitis C antigens, and the like.

Antigens, including antigenic peptides, can be bound to an antigenbinding cleft of an antigen presenting complex either actively orpassively, as described in U.S. Pat. No. 6,268,411 which is herebyincorporated by reference in its entirety. Optionally, an antigenicpeptide can be covalently bound to a peptide binding cleft.

If desired, a peptide tether can be used to link an antigenic peptide toa peptide binding cleft. For example, crystallographic analyses ofmultiple class I MHC molecules indicate that the amino terminus of β2Mis very close, approximately 20.5 Angstroms away, from the carboxylterminus of an antigenic peptide resident in the MHC peptide bindingcleft. Thus, using a relatively short linker sequence, approximately 13amino acids in length, one can tether a peptide to the amino terminus ofβ2M. If the sequence is appropriate, that peptide will bind to the MHCbinding groove (see U.S. Pat. No. 6,268,411).

The antibody or fragment and/or antigen presenting complexes may beconjugated to a solid support for ex vivo or in vivo antigenpresentation. Various solid supports are described in WO 2004/006951,the contents of which are hereby incorporated by reference in theirentirety. In some embodiments, the solid support is a bead or particlewith functional groups for coupling ligands. The material may be abiodegradable organic material, such as cellulose or dextran. In someembodiments, block co-polymers are selected to traffic to specificanatomical sites and biodegrade over specific intervals, that is, have alonger or shorter plasma half-life, or a longer or short tissueresidency time.

In some embodiments, the bead or particle comprises a polymer, such asone or more of cyclodextrin-containing polymers, cationiccyclodextrin-containing polymers, poly(D,L-lactic acid-co-glycolic acid)(PLGA), poly(caprolactone) (PCL), ethylene vinyl acetate polymer (EVA),poly(lactic acid) (PLA), poly(L-lactic acid) (PLLA), poly(glycolic acid)(PGA), poly(L-lactic acid-co-glycolic acid) (PLLGA), poly(D,L-lactide)(PDLA), poly(L-lactide) (PLLA). PLGA-b-poly(ethylene glycol)-PLGA(PLGA-bPEG-PLGA), PLLA-bPEG-PLLA, PLGA-PEG-maleimide (PLGA-PEG-mal),poly(D,L-lactide-co-caprolactone),poly(D,L-lactide-co-caprolactone-co-glycolide),poly(D,L-lactide-co-PEO-co-D,L-lactide),poly(D,L-lactide-co-PPO-co-D,L-lactide), polyalkyl cyanoacralate,polyurethane, poly-L-lysine (PLL), hydroxypropyl methacrylate (HPMA),polyethyleneglycol, poly-L-glutamic acid, poly(hydroxy acids),polyanhydrides, polyorthoesters, poly(ester amides), polyamides,poly(ester ethers), polycarbonates, polyalkylenes such as polyethyleneand polypropylene, polyalkylene glycols such as poly(ethylene glycol)(PEG), polyalkylene oxides (PEO), polyalkylene terephthalates such aspoly(ethylene terephthalate), polyvinyl alcohols (PVA), polyvinylethers, polyvinyl esters such as poly(vinyl acetate), polyvinyl halidessuch as poly(vinyl chloride) (PVC), polyvinylpyrrolidone, polysiloxanes,polystyrene (PS), polyurethanes, derivatized celluloses such as alkylcelluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters,nitro celluloses, hydroxypropylcellulose, carboxymethylcellulose,polymers of acrylic acids, such as poly(methyl(meth)acrylate) (PMMA),poly(ethyl(meth)acrylate), poly(butyl(meth)acrylate),poly(isobutyl(meth)acrylate), poly(hexyl(meth)acrylate),poly(isodecyl(meth)acrylate), poly(lauryl(meth)acrylate),poly(phenyl(meth)acrylate), poly(methyl acrylate), poly(isopropylacrylate), poly(isobutyl acrylate), poly(octadecyl acrylate)(polyacrylic acids), and copolymers and mixtures thereof, polydioxanoneand its copolymers, polyhydroxyalkanoates, polypropylene fumarate),polyoxymethylene, poloxamers, poly(ortho)esters, poly(butyric acid),poly(valeric acid), poly(lactide-co-caprolactone), trimethylenecarbonate, polyvinylpyrrolidone, polyorthoesters, polyphosphazenes, andpolyphosphoesters, and blends and/or block copolymers of two or moresuch polymers. Other pharmaceutically acceptable materials, such aslatex, may also be used as the solid particle support.

In some embodiments, the antigen-presenting complex and co-stimulatorysignal are conjugated to PLGA or PLGA-PEG particles having surfacefunctional groups on the terminal end of the polymer (e.g., the end thatfaces outward towards the surface of the particle), such asPLGA-PEG-maleimide particles, which provide functional groups forchemical coupling on the hydrophilic exterior surface. In someembodiments, the aAPCs persist in peripheral blood circulationsufficiently long to allow distribution to target tissues, includingtrafficking to lymph nodes via blood/lymph exchange. The composition ofthe shell may also impact biodistribution. Thus, in various embodimentsthe particles have a hydrophilic shell, which can be accomplished by thePEG of the PLGA-PEG co-polymer. In various embodiments, the charge ofthe particles is slightly negative, for example, due to the combinationof the COOH groups on the PLGA as well as by charge contributed by thetargeting ligands attached to the surface of the particle. In someembodiments, the particles (either with or without conjugated ligand)have a surface charge of from about 0 to about −20 mV, or in someembodiments −5 to −15 mV, or about −10 mV.

Nanoparticles comprising PLGA-PEG copolymers are described in U.S. Pat.No. 8,420,123, for example, which is hereby incorporated by reference.

The particles can vary from being irregular in shape to being sphericaland/or from having an uneven or irregular surface to having a smoothsurface. Spherical particles have less surface area relative toparticles of irregular size. If spherical particles are used, lessreagent is necessary due to the reduced surface area. On the other hand,an irregularly shaped particle has a significantly greater surface areathan a spherical particle, which provides an advantage for conjugatedprotein content per surface area and surface area contact for cells. Forexample, asymmetrical nanoparticles may have at least one surface havinga radius of curvature along at least one axis which is in one of thefollowing ranges: (a) about 1 nm to about 10 nm; (b) about 11 nm toabout 100 nm; (c) about 101 nm to about 400 nm; (d) about 401 nm toabout 1 μm; (e) about 10 μm to about 20 μm; (t) about 20 m to about 100μm; and (g) about 101 μm to about 1 mm. In some embodiments, theasymmetric nanoparticle may has an asymmetrical shape defined by adimension (a) along an x-axis, a dimension (b) along a y-axis, and adimension (c) along a z-axis, wherein at least one of (a), (b), or (c)is not equal to at least one other dimension (a), (b), or (c). In someembodiments, the asymmetrical shape is an ellipsoid, which can bedescribed by one of the following equations: a>b=c (prolate ellipsoid);a>b>c (tri-axial ellipsoid); and a=b>c (oblate ellipsoid). Asymmetricalnanoparticles that may be used in accordance with the invention aredescribed in WO 2013/086500, which is hereby incorporated by referencein its entirety.

The size of particles can vary. The particle size (nominal diameter) invarious embodiments is in the range from 0.05-50 μm, or in someembodiments 0.05-35 μm, or in some embodiments 0.05 to 10 μm, and insome embodiments is from about 0.05 to about 3.0, about 4.0, or about5.0 μm. For example, in some embodiments, the particles are 50 to 500 nmin diameter or average diameter. In some embodiments, the particles havean average size of less than about 400 nm, about 300 nm, about 200 nm,or about 100 nm, to allow for better peripheral blood circulation. Insome embodiments, the nanoparticles have an average size (e.g., diameteror largest axis) of about 100 nm, about 150 nm, or about 200 nm. Theterm “about”, when connected to a numerical feature, means ±10%. In someembodiments, at least 90% of the particles are in the range of about 50to about 250 nm, such as about 100 to about 150 nm. The particles can beuniform in size or can vary in size, with the average particle sizepreferably being as described above. In some embodiments, the particlesare sufficiently small to take advantage of the “EPR effect” (enhancedpermeability and retention effect).

Ligands and molecular complexes described herein can be chemicallyconjugated to the beads using any available process. Functional groupsfor ligand binding include PEG-COOH, PEG-NH2, PEG-SH or other functionalgroup attached to a different polymer such as polycyanoacrylate orpolycaprolactone.

For example, a solid support can be coated before proteins are bound toits surface. Once a coating chemistry has been chosen, the surface of asolid support can be activated to allow the specific attachment ofparticular protein molecules. Thus, coatings can be selected with a viewto optimal reactivity and biocompatibility with various cellpopulations. Preferably, whatever coating chemistry is used provides asuitable matrix for further activation chemistry. Numerous such coatingsare well known in the art. For example, solid supports can be coatedwith human serum albumin, tris (3-mercaptopropyl)-N-glycylamino) methane(U.S. Pat. No. 6,074,884), gelatin-aminodextrans (U.S. Pat. No.5,466,609), or amino acid homopolymers or random copolymers. In oneembodiment, a random amino acid copolymer comprising poly(glutamate,lysine, tyrosine) [6:3:1] is used; this copolymer is available fromSigma Chemical Co. as Product No. P8854. It is a linear random polymerof the amino acids glutamic acid, lysine, and tyrosine in a ratio of 6parts glutamic acid, 3 parts lysine, and 1 part tyrosine. In anotherembodiment, an amino acid copolymer is used that includes lysine andtyrosine in a ratio of 4 parts lysine to 1 part tyrosine. In yet anotherembodiment, an amino acid copolymer is used that includes lysine andalanine in a ratio of 1 part lysine to 1 part alanine. In anotherembodiment, a solid support is coated with a synthetic polymer, then thesynthetic polymer is activated before it is linked to a proteinmolecules.

In some embodiments, molecules are directly attached to solid supportsby adsorption or by direct chemical bonding, including covalent bonding.See, e.g., Hermanson, BIOCONJUGATE TECHNIQUES, Academic Press, New York,1996. A molecule itself can be directly activated with a variety ofchemical functionalities, including nucleophilic groups, leaving groups,or electrophilic groups. Activating functional groups include alkyl andacyl halides, amines, sulfhydryls, aldehydes, unsaturated bonds,hydrazides, isocyanates, isothiocyanates, ketones, and other groupsknown to activate for chemical bonding. Alternatively, a molecule can bebound to a solid support through the use of a small molecule-couplingreagent. Non-limiting examples of coupling reagents includecarbodiimides, maleimides, N-hydroxysuccinimide esters,bischloroethylamines, bifunctional aldehydes such as glutaraldehyde,anhydrides and the like. In other embodiments, a molecule can be coupledto a solid support through affinity binding such as abiotin-streptavidin linkage or coupling, as is well known in the art.For example, streptavidin can be bound to a solid support by covalent ornon-covalent attachment, and a biotinylated molecule can be synthesizedusing methods that are well known in the art.

In some embodiments, the particle or bead is a polymer, such asPLGA-PEG, PLGA-PEG-maleimide, or an ester-endcapped PLGA, in whichfunctional groups for conjugation of surface ligands are created duringpolymerization. The maleimide group provides the formed particles with ahydrophilic “stealth” coating (PEG) on the outer surface of the particleas well as functional groups attached to this shell that can be used forcovalent attachment of ligands that have at least one free sulfhydryl(—SH) group available. For example, HLA-1g ligands and/or anti-CD28 canbe constructed on a human IgG4 framework (as described herein) thatcontains a S473C substitution in the Fe. This unpaired cysteine residueat 473 of either HLA-Ig or anti-CD28 can be conjugated to the maleimidegroup attached to the PEG under mild reducing conditions. Mild reducingconditions are unlikely to irreversibly denature the proteins,especially the HLA-beta-2-microglobulin portion of the HLA-Ig molecule.

In an exemplary embodiment, the nanoparticles are in the range of fromabout 50 nm to as large as about 5 μm (e.g., the average diameter orlargest axis), have a core (PLGA) that can be tuned for a specificbiodegradation rate in vivo (by adjusting the LA:GA ratio and/or mw ofthe PLGA polymer), a hydrophilic outer shell that protects fromopsonization by serum proteins and removal from circulation (acting like“PEG brushes”), surface functionalized with consistent control of liganddensity (stochastic relationship of 1 molecule/maleimide group) andorientation of ligand away from the core. In some embodiments, the LA:GAratio is from 60%/40% to 40%/60%, and in some embodiments is about50%/50%. In some embodiments, the PLGA has a molecular weight of about25K to about 35K (e.g., about 30K), and the PEG has a molecular weightof about 3K to about 10K, such as about 5K. In some embodiments, thecore particle has a diameter of about 150 nm, or about 200 nm.

In an alternative embodiment, the support can be coated with a polymerthat contains one or more chemical moieties or functional groups thatare available for covalent attachment to a suitable reactant, typicallythrough a linker.

Activation chemistries allow for specific, stable attachment ofmolecules to the surface of solid supports. There are numerous methodsthat can be used to attach proteins to functional groups. For example,the common cross-linker glutaraldehyde can be used to attach proteinamine groups to an aminated solid support surface in a two-step process.The resultant linkage is hydrolytically stable. Other methods includeuse of cross-linkers containing n-hydro-succinimido (NHS) esters whichreact with amines on proteins, cross-linkers containing active halogensthat react with amine-, sulfhydryl-, or histidine-containing proteins,cross-linkers containing epoxides that react with amines or sulfhydrylgroups, conjugation between maleimide groups and sulfhydryl groups, andthe formation of protein aldehyde groups by periodate oxidation ofpendant sugar moieties followed by reductive amination.

The attachment of specific proteins to a solid support surface can beaccomplished by direct coupling of the protein or by using indirectmethods. Certain proteins will lend themselves to direct attachment orconjugation while other proteins or antibodies retain better functionalactivity when coupled to a linker or spacer protein such as anti-mouseIgG or streptavidin. If desired, linkers or attachment proteins can beused. Ligands, such as the antigen-presenting complexes andco-stimulatory molecules, may be modified with amino acid substitutionsto allow chemical conjugation.

The ratio of particular proteins on the same solid support can be variedto increase the effectiveness of the solid support in antigen orantibody presentation. For example, ratios of antigen presenting complexto anti-CD28 can be at least about 30:1, or at least about 10:1, about3:1, about 1:1, about 0.3:1; about 0.1:1, and at least about 0.03:1. Insome embodiments, the ratio is about 5:1, about 4:1, about 3:1, about2:1, or about 1:1, about 1:2, about 1:3, about 1:4, or about 1:5. Thetotal amount of protein coupled to the supports can be at least 10mg/ml, at least 25 mg/ml, at least 50 mg/ml, at least 100 mg/ml, atleast 150 mg/ml, or greater than 200 mg/ml. In some embodiments, such asthose employing PLGA or PLGA-PEG particles having surface functionalgroups (e.g., maleimide or ester), the total amount of protein coupledto the particles can be from 1 to 10 μg per mg of PLGA, or in someembodiments, from 2 to 6 μg per mg PLGA. In some embodiments, the liganddensity of the particles is from about 10³ to about 10⁵ ligands/μm², orabout 10⁴ ligands/μm² in some embodiments. For example, fornanoparticles in the range of 100 to 200 nm in size, the nanoparticleson average have about 100 to about 1500 ligands, such as about 200 toabout 1200 ligands, or about 400 to about 1000 ligands, or about 500 toabout 800 ligands.

In various embodiments, the invention provides a pharmaceuticalcomposition comprising a polymeric bead or particle, an anti-CD28antibody as described herein, and/or a antigen-presenting complex, suchas humanized Ig HLA fusion complex as described herein. Thepharmaceutical composition may further comprise an antigenic peptide forpresentation to T cells as described, and which may be co-formulatedwith the conjugated bead or particle. In various embodiments, thepharmaceutical composition is shelf stable, and in some embodiments, isprovided in lyophilized form for reconstitution prior to administration,or provided in another “off-the-shelf” pharmaceutical preparation.

In some embodiments, the invention provides a pharmaceutical compositioncomprising PLGA or PLGA-PEG based nanoparticles, of from 50 to 500 nm indiameter or average diameter, and comprising surface-conjugatedanti-CD28 antibodies and antigen-presenting complexes. The anti-CD28antibody can be a humanized antibody, e.g., as described herein, and maybe an antibody fragment such as a single chain variable fragment. Theantigen presenting complex in some embodiments comprises at least oneHLA antigen-binding cleft. The anti-CD28 and HLA complex can be coupledto the particles separately or together in the same reaction. Thepharmaceutical composition can include at least one peptide antigen,such as a tumor antigen (e.g., MART-1), and which may be co-formulatedwith the particles without any active loading process.

The pharmaceutical compositions described herein are useful forimmunotherapy, for example, in methods for inducing the formation ofantigen-specific cytotoxic T cells, by administering an effective amountof the composition to a patient in need. In some embodiments, thepatient is a cancer patient.

The particle-based antigen presenting platforms described herein can beadministered to patients by any appropriate routes, includingintravenous administration, intra-arterial administration, subcutaneousadministration, intradermal administration, intralymphaticadministration, and intra-tumoral administration. Patients include bothhuman and veterinary patients.

Some exemplary embodiments the invention are described below.

In some embodiments the invention provides a pharmaceutical compositionthat comprises polymeric PLGA-PEG particles having a size in the rangeof about 100 to 200 nm, a surface charge of about −0 to −20 mV (and −5to −15 mV in some embodiments), and from about 100 to 1500 proteinligands per particle. The protein ligands in some embodiments are eachcoupled to the particle through a sulfhydryl-maleimide chemistry. Theligands comprise a population of anti-CD28 antibody ligands, and apopulation of HLA ligands and one or more antigenic peptides forpresentation to T cells. The composition comprises a pharmaceuticallyacceptable carrier for intravenous, intra-arterial, subcutaneous,intradermal, intralymphatic, or intra-tumoral administration.

In some embodiments, the particles are substantially spherical or aboutspherical.

In some embodiments, the PLGA is a polymer of about 50% lactic acid (LA)and 50% glycolic acid (GA).

In some embodiments, the PLGA polymer has a molecular weight of about30K, and the PEG has a molecular weight of about 3K to about 10K, suchas about 5K.

In some embodiments, the composition has from 400 to 1000 ligands perparticle.

In some embodiments, the anti-CD28 antibody ligands comprise a humanIGHV4-59 germline framework optionally having from 5 to 15 murineframework residues, and a IGKV4-01 germline framework optionally havingfrom 3 to 15 murine framework residues.

In some embodiments, the anti-CD28 is a ScFv.

In some embodiments, the HLA is HLA-A*02:01, which may comprise a fusionto immunoglobulin sequences above the hinge region sufficient to providea dimeric HLA construct.

In some embodiments, the composition is lyophilized.

In particular, antigen presenting platforms can be useful for treatingpatients with infectious diseases, cancer, or autoimmune diseases, or toprovide prophylactic protection to immunosuppressed patients.

Infectious diseases that can be treated include those caused bybacteria, viruses, prions, fungi, parasites, helminths, etc. Suchdiseases include AIDS, hepatitis, CMV infection, and post-transplantlymphoproliferative disorder (PTLD). CMV, for example, is the mostcommon viral pathogen found in organ transplant patients and is a majorcause of morbidity and mortality in patients undergoing bone marrow orperipheral blood stem cell transplants (Zaia, Hematol. Oncol. Clin.North Am. 4, 603-23, 1990). This is due to the immunocompromised statusof these patients, which permits reactivation of latent virus inseropositive patients or opportunistic infection in seronegativeindividuals. Current treatment focuses on the use of antiviral compoundssuch as gancyclovir, which have drawbacks, the most significant beingthe development of drug-resistant CMV. A useful alternative to thesetreatments is a prophylactic immunotherapeutic regimen involving thegeneration of virus-specific CTL derived from the patient or from anappropriate donor before initiation of the transplant procedure.

PTLD occurs in a significant fraction of transplant patients and resultsfrom Epstein-Barr virus (EBV) infection. EBV infection is believed to bepresent in approximately 90% of the adult population in the UnitedStates (Anagnostopoulos & Hummel, Histopathology 29, 291-2) 15, 1996).Active viral replication and infection is kept in check by the immunesystem, but, as in cases of CMV, individuals immunocompromised bytransplantation therapies lose the controlling T cell populations, whichpermits viral reactivation. This represents a serious impediment totransplant protocols. EBV may also be involved in tumor promotion in avariety of hematological and non-hematological cancers. There is also astrong association between EBV and nasopharyngeal carcinomas. Thus aprophylactic treatment with EBV-specific T cells offers an excellentalternative to current therapies.

Cancers that can be treated according to the invention include melanoma,carcinomas, e.g., colon, head and neck cancer, duodenal, prostate,breast, lung, ovarian, ductal, colon, hepatic, pancreatic, renal,endometrial, stomach, dysplastic oral mucosa, polyposis, invasive oralcancer, non-small cell lung carcinoma, transitional and squamous cellurinary carcinoma etc.; neurological malignancies, e.g., neuroblastoma,gliomas, etc.; hematological malignancies, e.g., chronic myelogenousleukemia, childhood acute leukemia, non-Hodgkin's lymphomas, chroniclymphocytic leukemia, malignant cutaneous T-cells, mycosis fungoides,non-MF cutaneous T-cell lymphoma, lymphomatoid papulosis, T-cell richcutaneous lymphoid hyperplasia, bullous pemphigoid, discoid lupuserythematosus, lichen planus, etc.; and the like. See, e.g., Mackensenet al, Int. J. Cancer 86, 385-92, 2000; Jonuleit et al., Int. J. Cancer93, 243-51, 2001; Lan et al., J. Immunotherapy 24, 66-78, 2001;Meidenbauer et al, J. Immunol. 170(4), 2161-69, 2003.

In some embodiments, the invention provides a method for treatingcancer, including those cancers identified above, through administrationof the pharmaceutical composition described herein to activate T-cellshaving anti-tumor activity. In some embodiments, the therapy is providedtogether with one or more immune checkpoint inhibitors, such asNivolumab, Pembrolizumab, and Ipilimumab. In some embodiments, theadditional therapy is anti-CTLA4 or anti-PD1, or anti-PD-L1. Theadditional therapy or checkpoint inhibitor may be administeredseparately through its conventional regimen, or may be administered asan additional ligand to the nanoparticles described herein, or attachedto a separate population of nanoparticles. In some embodiments, the oneor more immune checkpoint inhibitors are provided as initial therapy,and therapy with the nanoparticles described herein initiatedsubsequently, for example, after from about 1 to about 8 weeks ofcheckpoint inhibitor therapy, or after about 2 to about 4 weeks ofcheckpoint inhibitor therapy. In some embodiments, the one or morecheckpoint inhibitors are provided concomitantly with the nanoparticletherapy, for example at initiation of therapy and about every two weeks,or at initiation of therapy and about every two weeks for the one ormore checkpoint inhibitors and about every four weeks for thenanoparticle therapy. In some embodiments, the patient is resistant orshows only a partial or transient response to checkpoint inhibitortherapy, and the aAPCs described herein enhance tumor regression inthese patient. In still other embodiments, for cancers that aretypically resistant to checkpoint inhibitor therapy, the compositionsdescribed herein expand the successful use of checkpoint inhibitors tosuch cancers.

In some embodiments, the peptide antigen is selected in a personalizedbasis for the patient, based on an analysis of the patient's tumor. Forexample, a process described by Ionov Y., A high throughput method foridentifying personalized tumor-associated antigens, Oncotarget1(2):148-155 (2010) (which is hereby incorporated by reference) may beused, or other process. In these embodiments, the nanoparticles can beprovided (on an “off-the shelf” basis), and tumor antigens selected andloaded in a personalized basis.

Autoimmune diseases that can be treated include asthma, systemic lupuserythematosus, rheumatoid arthritis, type I diabetes, multiplesclerosis, Crohn's disease, ulcerative colitis, psoriasis, myastheniagravis, Goodpasture's syndrome, Graves' disease, pemphigus vulgaris,Addison's disease, dermatitis herpetiformis, celiac disease, andHashimoto's thyroiditis.

Antigen-specific helper T cells can be used to activate macrophages orto activate B cells to produce specific antibodies that can be used, forexample, to treat infectious diseases and cancer. Antibody-producing Bcells themselves also can be used for this purpose.

The invention further provides polynucleotides encoding the amino acidsequences described herein, as well as host cells expressing the same.

This invention is further illustrated by the following non-limitingexamples.

EXAMPLES Example 1: Design of Germline Humanized Variable Regions andHuman Constant Region Sequences

This Example demonstrates, inter alia, a design of sequences forgermline humanized (CDR grafted) antibodies from a mouse anti-CD28antibody template; a design of human constant region sequences includinghuman IgG4 containing the S241P (Kabat numbering) hinge stabilizingmutation, the L248E (Kabat numbering) mutation to remove residual Fegamma receptor binding and a Cys residue (S473C, Kabat numbering)suitable for coupling the antibody; a design of a variant germlinehumanized antibody V domain with potential non-binding to CD28; a designof a linker sequence for the fusion of HLA-A*02:01 to the N-terminus ofthe germline humanized antibodies that does not contain potential T cellepitopes.

The starting anti-CD28 antibody was the murine 9.3 monoclonal antibody(Tan et al., J. Exp. Med. 1993 177:165). Structural models of the 9.3antibody V regions were produced using Swiss PDB and analyzed in orderto identify amino acids in the V regions that were likely to beessential for the binding properties of the antibody. All residuescontained within the CDRs (using both Kabat and Chothia definitions)together with a number of framework residues were considered to be ofpotential importance for binding. Both the VH and Vκ sequences ofanti-CD28 contain typical framework (Fw) residues and the CDR 1, 2 and 3motifs are comparable to many murine antibodies.

For humanization, the human IGHV4-59 germline Fw was selected as atemplate for the heavy chain (in preference to the IGHV3/OR16-10selected by Tan et al. J. Immunol 2002 169:1119-1125). The IGKV4-01germline Fw was selected as a template for the light chain. These Fwsboth have 62% homology to their respective murine VH and Vκ sequences.The murine CDRs were grafted into these Fws and varying numbers ofmurine Fw residues were also included to create three humanized VHvariants and three humanized Vκ variants (FIGS. 1-6).

For the heavy chain Fw, Fw1 residues 1 and 3 were thought to beimportant for antigen binding since they are adjacent to the bindingpocket, while residue 6 was considered to affect the conformation ofboth the beta strand supporting residues 1 and 3 and the conformation ofCDR3. Therefore these murine Fw residues were retained in all variants.

In Fw2, residue 37 was considered to be important for maintaining theinterface between the VH and Vκ, while residue 48 was considered tosupport the conformation of CDR2; therefore both of these residues wereretained in all variants.

In Fw3, residues 73, 76 and 78 directly contact CDR1, while residue 71contacts both CDR1 and CDR2; therefore these residues are likely to berequired for antigen binding (depending upon the contribution of CDR1and CDR2) and were therefore retained in all variants. Residue 71 cansometimes indirectly affect the conformation of CDR1 by influencing theconformation of residues 71 to 78, while residues 82a and 82c may alsoindirectly influence the conformation of CDR2. These residues weretherefore retained in VH1 only. Residues 67 and 82 are adjacent in thethree dimensional structure and interact to fill space which can affectthe conformation of CDR2 and potentially influence the beta strandssupporting CDRs 1 and 3. Therefore these residues were retained invariants VH1 and VH2.

For the light chain Fw, Fw1 residue 3 is adjacent to the binding pocketand can be directly involved in antigen binding, while residue 4directly supports the conformation of CDR3. Therefore these murine Fwresidues were retained in all variants.

In Fw2, residue 49 supports the conformation of CDR2 and is alsocritical for the interface between the heavy and light chains where itdirectly supports the conformation of heavy chain CDR3, thus wasretained in all variants.

In Fw3, residues 85 and 87 were considered important for the interfaceof the heavy and light chains and also to support the conformation ofCDR3 and were therefore retained in all variants. Residue 80 wasconsidered to potentially have indirect effects on the conformation ofCDRs 2 and 3 and was retained in Vκ1 only. Residue 70 commonly saltbridges with light chain residue R24 and therefore has importantconformational effects upon the Vκ domain. In anti-CD28, this saltbridge is absent (since residue 70 is N rather than D) and introducingthis interaction could be disadvantageous; however in the murineantibody N70 is glycosylated (NFS) and it would be beneficial to removethis during humanization; therefore the murine N was retained in Vκ1 andVκ2, but changed to D in Vκ3.

Constant region sequences based upon human IgG4/κ were designed toincorporate a hinge stabilizing mutation (S241P) and a mutation in thelower hinge that removes residual Fc gamma receptor binding (L248E). Acysteine residue was also included near the C-terminus of the Fc forchemical coupling purposes (S473C). The modified IgG4 heavy chainconstant region sequence is shown in FIG. 7, together with the κ lightchain constant region sequence (FIG. 8).

A further VH domain was designed for potential non-binding to CD28 andthis sequence is shown in FIG. 9. Analysis of the murine V regionsequences suggested (from the extent of somatic mutation of mousegermline V regions) that the VH was likely to the major contributor toCD28 binding. Therefore only a potential non-binding humanized VHvariant was designed. This variant does not contain any mouse Fwresidues to reconstitute the correct CDR conformations and also containsthree mutations in CDRH3 at residues that are likely to be critical forbinding (Y100A, Y100aA, Y100bA).

Example 2: Design of Linkers for Fusion of HLA-A*02:01 to HumanizedAntibodies

Linkers for the fusion of HLA-A*02:01 (IMGT Accession No. HLA00005) tothe N-terminus of humanized anti-CD28 antibodies were constructed andincorporated analysis by iTope™ and TCED™ to remove potentialimmunogenicity.

The iTope™ software predicts favorable interactions between amino acidside chains of a peptide and specific binding pockets (in particularpocket positions; p1, p4, p6, p7 and p9) within the open-ended bindinggrooves of 34 human MHC class II alleles. These alleles represent themost common HLA-DR alleles found world-wide with no weighting attributedto those found most prevalently in any particular ethnic population.Twenty of the alleles contain the ‘open’ p1 configuration and fourteencontain the ‘closed’ configuration where glycine at position 83 isreplaced by a valine. The location of key binding residues is achievedby the in silico generation of 9mer peptides that overlap by one aminoacid spanning the test protein sequence. Comparisons with physical MHCclass II binding experiments has shown that iTope™ can be used tosuccessfully discriminate with high accuracy between peptides thateither bind or do not bind MHC class II molecules. Any limitations of insilico MHC class II binding analysis are reduced using the TCED™ whichcontains the sequences of a large database of peptides (>10,000peptides) derived from sequences previously screened in EpiScreen™ exvivo T cell epitope mapping assays. The TCED™ can thus be used to searchany test sequence against unrelated antibody and protein sequences tofind correlations with actual ex vivo immunogenicity.

Analysis of the linker sequences using iTope™ was performed withoverlapping 9 mers spanning the linker sequences which were testedagainst each of the 34 MHC class II alleles. Each 9mer was scored basedon the potential ‘fit’ and interactions with the MHC class II molecules.The peptide scores calculated by the software lie between 0 and 1.Non-germline peptides that produced a high mean binding score (>0.55 inthe iTope™ scoring function) were highlighted and, if ≥50% of the MHCclass II binding peptides (i.e. 17 out of 34 alleles) had a high bindingaffinity (score >0.6), such peptides were defined as “promiscuous highaffinity” MHC class II binding peptides (which are considered a highrisk for containing CD4+ T cell epitopes). Peptides with 250% of the MHCclass II binding peptides with a score >0.55 (but without amajority >0.6) were defined as “promiscuous moderate affinity” MHC classII binding peptides. Further analysis of the sequences was performedusing the TCED™. The sequences were used to interrogate the TCED™ byBLAST search in order to identify any high sequence homology betweenpeptides (T cell epitopes) from unrelated proteins that stimulated Tcell responses in previous EpiScreen™ studies.

The sequences used by Schneck et al. incorporated two linkers, one atthe N-terminus of HLA-A*02:01 to link with an N-terminal signal sequenceand one at the C-terminus for fusion to the anti-CD28 VII domain (SeeFIG. 9 for example). For the N-terminal linker, sequence was analyzedfrom the signal sequence cleavage site through the linker and includingthe first 8 amino acids of HLA-A*02:01 mature protein. For theC-terminal linker, sequence was analyzed from the terminal 8 amino acidsof HLA-A*02:01 α3 domain, through the linker sequence and up to thefirst 8 amino acids of the anti-CD28 VH domain.

Peptides with binding scores >0.6 (high affinity) bind to the majority(≥17) of MHC class II alleles (termed promiscuous high affinity binder).Moderate affinity binders with a binding score between 0.55 and 0.6 bind≥17 MHC class II alleles. The N-terminal linker was found to contain twopromiscuous MHC class II binding sequences, one high affinity (with p1anchor at position 2) and one moderate affinity (with p1 anchor atposition 4). The C-terminal linker was found to contain one promiscuousmoderate affinity MHC class II binding peptide with p1 anchor atposition 11.

A BLAST search of Antitope's T cell epitope database (TCED™) was carriedout using the same sequences as used in the iTope™ analysis to determineany homology with previously identified epitopes. The TCED™ is used tosearch any test sequence against a large (>10,000 peptides) database ofpeptides derived from unrelated sequences which have been tested inEpiScreen™ T cell epitope mapping assays. Neither of the linkersequences was found to contain any ‘hits’ in the TCED™.

iTope™ was further used to assess sequence changes to the linkers inorder to reduce their propensity for binding to MHC class II. It wasnoted that the N-terminal linker could be removed entirely such that theN-terminus of HLA-A*02:01 is fused directly either to the signalsequence provided in the pBFKsr vector or to its natural signalsequence. This would ensure that the N-terminus of the fusion proteinwould contain only human germline sequence and avoid the risk of T cellepitopes. The recommended linker sequences below were found to reduceMHC class II binding to background residual levels (<5 of the allelesbound by any 9mer), and to provide suitable restriction sites forcloning (although both sequences will require modification of thevector):

Example 3: Codon Optimization of Sequences and Expression Cloning

Codons were optimized using GeneOptimizer®, and optimized sequences werecloned for expression as shown below.

Sequences were engineered with PmeI restriction sites, Kozak sequence,and signal peptide for expression in NS0 cells. Translation startsimmediately downstream of the Kozak sequence.

The full translated amino acid sequence of the HLA-IgG4HC fusion isshown in FIG. 10.

The translated sequence of LC3 (VK3) is shown in FIG. 11.

The translated sequence for HC1 is shown in FIG. 12.

The translated sequence for HC2 is shown in FIG. 13.

Human 32 microglobulin was also expressed.

Example 4: Expression in NS0 Cells

Based on Biacore affinity data and other considerations, the HC1::LC3and HC2::LC3 heavy chain and light chain combinations were selected asthe primary and secondary mAb candidates, respectively, forStableFast-NS0 cell line development.

The final vector map for the pBFksr::HC1::LC3 bicistronic expressionvector for STABLEFAST-NS0 cell line generation is depicted in FIG. 14.Construction of pBFksr::HC2::LC3 was done using the same approaches.

Parental NS0 cells were expanded in supplemented serum-free growthmedium. Upon establishment of health culture, ten million cells (10×10⁶)were transfected with 45 μg linearized (ΔPvuI) expression vector DNA.Cells were allowed to recover for 24 hours in bulk in growth medium.Following recovery, cells were washed in supplemented serum-freeselective medium (cholesterol-), resuspended in the selective medium anddistributed to 40×96-well plates at 200 μL per well. Actual distributionwas 1140 cells/well and 840 cells/well for HC1::LC3 and HC2::LC3,respectively. Plates were incubated at 37° C., 5% CO2 for 1 week and fedwith phenol red supplemented selective medium. At two weekspost-transfection, numerous wells were actively growing based on mediumcolor change from red to yellow.

A total of 1.127 wells from the HC1::LC3 transfection were screened forhuman IgG expression by ELISA. A total of 612 wells from the HC2::LC3transfection were screened. Based on IgG concentration, a total of 290and 101 cell lines were scaled up to 24-well plates for HC1::LC3 andHC2::LC3, respectively. A 24-hour productivity assay was used to selectbest expressers for further analysis. Briefly, 24-well plates wereseeded at 5×10⁵ cells in 500 μL fresh medium. After 24 hours,supernatants were screened by ELISA. Based on IgG concentration, a totalof 60 and 24 cell lines were scaled up to 6-well plates for HC1::LC3 andHC2::LC3, respectively.

A 3-day specific productivity assay was used to select best expressersfor further analysis. Briefly, 6-well plates were seeded at 4×105 cellsin 1.5 mL fresh medium. After 3 days, cells were counted andsupernatants were screened by ELISA. Based on IgG concentration andgrowth, the average specific productivity rate or SPR in pg/cell/day canbe calculated. Based on relative SPR, a total of 20 and 10 cell lineswere scaled up to T-75 flasks for HC1::LC3 and HC2::LC3, respectively.The 3-day SPR assay was repeated at the T-75 scale to select the finalcell lines for suspension adaptation and scale up for mAb production.

Five cell lines for each mAb were scaled up to 30-mL shaker culture andre-evaluated for SPR and growth. All suspension lines were banked. Thebest performing cell line for each mAb was scaled to spinner culture forsmall scale production.

For the HLA-IgG4 Fusion Protein, the pBFksr::HLA-IgG4::LC3 bicistronicexpression vector was constructed for STABLEFAST-NS0 cell linegeneration. The vector map is shown in FIG. 15. An expression cassetteand vector containing the human 32 microglobulin gene was also createdfor a tricistronic expression vector that encodes all three fusionprotein subunits (human HLA-IgG4 heavy chain fusion, a-CD28 light chain[LC3], and human β2 microglobulin). The tricistronic construct is shownin FIG. 16. Expression of all three genes was confirmed in transientHEK293 culture by ELISA and western blot analyses of supernatant.

Example 5: Functional Characterization

The humanized monoclonal antibody against CD28 was tested for itsability to induce expansion of freshly isolated PBMCs on mAb coatedplates. As shown in FIG. 17, the humanized anti-CD28 is not a superagonist.

The humanized monoclonal antibody was tested for its ability to stainCD28 on a human T-cell line. The results are shown in FIG. 18. FIG.18(A) shows staining with murine anti-human CD8 mAb (clone 9.3, IsotypeIgG2a). Black=unstained cells, red=anti-IgG2a FITC,blue=anti-CD28+anti-IgG2a FITC. FIG. 18(B) shows staining with humanizedanti-CD28 (isotype IgG4). Black=unstained cells, red=anti-IgG4 PE,blue=anti-CD28 (35 ng)+anti-IgG4 PE, purple=antiCD28 (1 μg)+anti-IgG4PE. The staining with humanized anti-CD28 can be blocked with Clone 9.3mAb (not shown).

After purification of I-LA-Ig, the antigen peptide loading efficiency ischecked by ELISA using conformation dependent anti-HLA mAb to capturethe peptide loaded protein (as described in Current protocols inImmunology Chapter 17.2). Reproducible loading efficiencies of ˜90% forspecific peptides (i.e. correct MHC restriction) is anticipated,compared to 0% for non-specific peptides (i.e. MHC mis-match).

INCORPORATION BY REFERENCE

All patents and publications referenced herein are hereby incorporatedby reference in their entireties.

What is claimed is:
 1. A pharmaceutical composition comprising:polymeric PLGA-PEG particles having a size in the range of about 100 to200 nm, a surface charge of about 0 to −20 mV, and from about 100 to1500 protein ligands per particle, the protein ligands optionallycoupled through a sulfhydryl-maleimide chemistry; a population ofanti-CD28 antibody ligands; a population of HLA ligands; one or moreantigenic peptides for presentation to T cells; and a pharmaceuticallyacceptable carrier for intravenous, intra-arterial, subcutaneous,intradermal, intralymphatic, or intra-tumoral administration.
 2. Thepharmaceutical composition of claim 1, wherein the particles aresubstantially spherical or about spherical.
 3. The pharmaceuticalcomposition of claim 1 or 2, wherein the PLGA is a polymer of about 50%lactic acid (LA) and 50% glycolic acid (GA).
 4. The pharmaceuticalcomposition of any one of claims 1 to 3, wherein the PLGA polymer has amolecular weight of from about 25K to about 35K, and the PEG has amolecular weight of from about 3K to about 10K.
 5. The pharmaceuticalcomposition of any one of claims 1 to 4, having from 400 to 1000 ligandsper particle.
 6. The pharmaceutical composition of any one of claims 1to 5, wherein the anti-CD28 antibody ligands comprise a human IGHV4-59germline framework optionally having from 5 to 15 murine frameworkresidues, and a IGKV4-01 germline framework optionally having from 3 to15 murine framework residues.
 7. The pharmaceutical composition of anyone of claims 1 to 5, wherein the anti-CD28 ligand is an antigen-bindingantibody fragment.
 8. The pharmaceutical composition of any one ofclaims 1 to 7, wherein the anti-CD28 ligand comprises a scFv.
 9. Thepharmaceutical composition of any one of claims 1 to 8, wherein the HLAligand is dimeric.
 10. The pharmaceutical composition of claim 9,wherein the HLA is HLA-A*02:01.
 11. The pharmaceutical composition ofclaim 9 or 10, wherein the HLA comprises an immunoglobulin fusion. 12.The pharmaceutical composition of claim 11, wherein the anti-CD28antibody ligand and the HLA-A*02:01 immunoglobulin fusion have an IgG4constant region with mutations at S241 and L248, and a Cysteine at codon473.
 13. The pharmaceutical composition of claim 12, wherein theanti-CD28 antibody ligands are conjugated to the particles through theCysteine at codon 473 of the immunoglobulin heavy chain.
 14. Thepharmaceutical composition of claim 12 or 13, wherein the HLA ligandsare conjugated to the particles through the Cysteine at codon 473 of theimmunoglobulin heavy chain.
 15. The pharmaceutical composition of claim1, wherein the HLA ligands comprise an extracellular domain of HLA, andare HLA monomers linked to the particle through a peptide or chemicallinker attached to the C-terminus of the HLA extracellular domain, andwherein the HLA is optionally HLA-A2.
 16. The pharmaceutical compositionof claim 1, wherein the HLA ligands comprise an extracellular domain ofHLA, and are HLA monomers linked to both a scFv of an anti-CD28 ligandand the particle through one or more peptide or chemical linkers, andwherein the HLA is optionally HLA-A2.
 17. The pharmaceutical compositionof any one of claims 1 to 16, wherein the composition is lyophilized.18. An anti-CD28 antibody or portion thereof, comprising a human IGHV4heavy chain amino acid sequence optionally with from one to fifteenamino acid modifications, wherein at least one complementaritydetermining region (CDR) is based on a murine antibody amino acidsequence.
 19. The antibody of claim 18, wherein the CDRs are based onmouse 9.3 mAb.
 20. The antibody of claim 18 or 19, wherein the heavychain is a variant of a human IGHV4-59 germline framework (FW).
 21. Theantibody of any one of claims 18 to 20, wherein the antibody comprises alight chain and the light chain comprises a variant of a human IGKV4-01FW.
 22. The antibody of any one of claims 18 to 21, wherein the heavychain comprises one or more of murine Fw residues at positions selectedfrom 1, 3, 6, 37, 48, 67, 71, 73, 76, 78, 82, 82a, and 82c.
 23. Theantibody of claim 22, wherein the light chain comprises one or moremurine Fw residues at positions selected from 3, 4, 49, 70, 85, 87, and80.
 24. The antibody of any one of claims 18 to 23, wherein the antibodycomprises a constant region or portion thereof, and the constant regionis optionally a variant of human IgG4.
 25. The antibody of claim 24,wherein the constant region comprises one or more hinge stabilizingmutations.
 26. The antibody of claim 25, wherein the hinge stabilizingmutation comprises one or more mutations introduced in the CH chain. 27.The antibody of claim 26, wherein the one or more mutations introducedin the CH chain includes S241P.
 28. The antibody of any one of claims 18to 27, wherein the antibody comprises a constant region and the constantregion comprises one or more mutations suitable for chemical couplingthe antibody to a solid support.
 29. The antibody of claim 28, whereinthe one or more mutations suitable for coupling create an unpairedcysteine.
 30. The antibody of claim 29, wherein the unpaired cysteine isS473C.
 31. The antibody of claim 29 or 30, wherein the unpaired cysteineprovides for a covalent attachment to a solid support.
 32. The antibodyof any one of claims 18 to 31, wherein the solid support is a bead orparticle, optionally with functional groups, which are optionallyesters, carboxylic acids, maleimides, alcohols, available for covalentbonding.
 33. The antibody of claim 32, wherein the bead or particlecomprises a polymer selected from one or more of cyclodextrin-containingpolymers, cationic cyclodextrin-containing polymers, poly(D,L-lacticacid-co-glycolic acid) (PLGA), poly(caprolactone) (PCL), ethylene vinylacetate polymer (EVA), poly(lactic acid) (PLA), poly(L-lactic acid)(PLLA), poly(glycolic acid) (PGA), poly(L-lactic acid-co-glycolic acid)(PLLGA), poly(D,L-lactide) (PDLA), poly(L-lactide) (PLLA),PLGA-b-poly(ethylene glycol)-PLGA (PLGA-bPEG-PLGA), PLLA-bPEG-PLLA,PLGA-PEG-maleimide (PLGA-PEG-mal), poly(D,L-lactide-co-caprolactone),poly(D,L-lactide-co-caprolactone-co-glycolide),poly(D,L-lactide-co-PEO-co-D,L-lactide),poly(D,L-lactide-co-PPO-co-D,L-lactide), polyalkyl cyanoacralate,polyurethane, poly-L-lysine (PLL), hydroxypropyl methacrylate (HPMA),polyethyleneglycol, poly-L-glutamic acid, poly(hydroxy acids),polyanhydrides, polyorthoesters, poly(ester amides), polyamides,poly(ester ethers), polycarbonates, polyalkylenes such as polyethyleneand polypropylene, polyalkylene glycols such as poly(ethylene glycol)(PEG), polyalkylene oxides (PEO), polyalkylene terephthalates such aspoly(ethylene terephthalate), polyvinyl alcohols (PVA), polyvinylethers, polyvinyl esters such as poly(vinyl acetate), polyvinyl halidessuch as poly(vinyl chloride) (PVC), polyvinylpyrrolidone, polysiloxanes,polystyrene (PS), polyurethanes, derivatized celluloses such as alkylcelluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters,nitro celluloses, hydroxypropylcellulose, carboxymethylcellulose,polymers of acrylic acids, such as poly(methyl(meth)acrylate) (PMMA),poly(ethyl(meth)acrylate), poly(butyl(meth)acrylate),poly(isobutyl(meth)acrylate), poly(hexyl(meth)acrylate),poly(isodecyl(meth)acrylate), poly(lauryl(meth)acrylate),poly(phenyl(meth)acrylate), poly(methyl acrylate), poly(isopropylacrylate), poly(isobutyl acrylate), poly(octadecyl acrylate)(polyacrylic acids), and copolymers and mixtures thereof, polydioxanoneand its copolymers, polyhydroxyalkanoates, polypropylene fumarate),polyoxymethylene, poloxamers, poly(ortho)esters, poly(butyric acid),poly(valeric acid), poly(lactide-co-caprolactone), trimethylenecarbonate, polyvinylpyrrolidone, polyorthoesters, polyphosphazenes, andpolyphosphoesters, and blends and/or block copolymers of two or moresuch polymers.
 34. The antibody of any one of claims 18 to 33,comprising a constant region, wherein the constant region comprises oneor more mutations to reduce Fc gamma receptor binding.
 35. The antibodyof claim 34, wherein the one or more mutations to reduce Fc gammareceptor binding comprise one or more mutations introduced in the CHchain.
 36. The antibody of claim 35, wherein the one or more mutationsintroduced in the CH chain includes L248E.
 37. The antibody of any oneof claims 18 to 36, wherein the antibody is conjugated to a solidsupport with molecular complexes presenting antigen for recognition by Tcells.
 38. An antigen presenting complex comprising a humanizedimmunoglobulin heavy chain sequence fused to an HLA amino acid sequence,wherein the complex optionally does not contain an immunoglobulin lightchain sequence.
 39. The antigen presenting complex of claim 36, whereinthe HLA-Ig fusion is dimeric.
 40. The antigen presenting complex ofclaim 38 or 39, wherein the immunoglobulin sequence comprises an IGV4sequence.
 41. The antigen presenting complex of any one of claims 38 to40, wherein the HLA amino acid sequence is HLA-A*02:01 (IMGT AccessionNo. HLA00005) or a derivative thereof.
 42. The antigen presentingcomplex of any one of claims 38 to 41, further comprising a linkerbetween the HLA and immunoglobulin sequences.
 43. The antigen presentingcomplex of any one of claims 38 to 42, further comprising an antigenicpeptide bound to the HLA for presentation to T cells.
 44. The antigenpresenting complex of claim 43, wherein the antigenic peptide is one ormore of tyrosinase, MAGE-A1, MAGE-A3, gp100, Melan A/Mart-1, gp75/brown,BAGE, NY-ESO-1, and S-100.
 45. The antigen presenting complex of any oneof claims 38 to 44, wherein the polypeptide is attached to solidsupport, which is optionally a bead or particle.
 46. The antigenpresenting complex of claim 45, wherein the bead or particle comprises apolymer selected from one or more of cyclodextrin-containing polymers,cationic cyclodextrin-containing polymers, poly(D,L-lacticacid-co-glycolic acid) (PLGA), poly(caprolactone) (PCL), ethylene vinylacetate polymer (EVA), poly(lactic acid) (PLA), poly(L-lactic acid)(PLLA), PLGA-b-poly(ethylene glycol)-PLGA (PLGA-bPEG-PLGA),PLLA-bPEG-PLLA, PLGA-PEG-maleimide (PLGA-PEG-mal), poly(glycolic acid)(PGA), poly(L-lactic acid-co-glycolic acid) (PLLGA), poly(D,L-lactide)(PDLA), poly(L-lactide) (PLLA), poly(D,L-lactide-co-caprolactone),poly(D,L-lactide-co-caprolactone-co-glycolide),poly(D,L-lactide-co-PEO-co-D,L-lactide),poly(D,L-lactide-co-PPO-co-D,L-lactide), polyalkyl cyanoacralate,polyurethane, poly-L-lysine (PLL), hydroxypropyl methacrylate (HPMA),polyethyleneglycol, poly-L-glutamic acid, poly(hydroxy acids),polyanhydrides, polyorthoesters, poly(ester amides), polyamides,poly(ester ethers), polycarbonates, polyalkylenes such as polyethyleneand polypropylene, polyalkylene glycols such as poly(ethylene glycol)(PEG), polyalkylene oxides (PEO), polyalkylene terephthalates such aspoly(ethylene terephthalate), polyvinyl alcohols (PVA), polyvinylethers, polyvinyl esters such as poly(vinyl acetate), polyvinyl halidessuch as poly(vinyl chloride) (PVC), polyvinylpyrrolidone, polysiloxanes,polystyrene (PS), polyurethanes, derivatized celluloses such as alkylcelluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters,nitro celluloses, hydroxypropylcellulose, carboxymethylcellulose,polymers of acrylic acids, such as poly(methyl(meth)acrylate) (PMMA),poly(ethyl(meth)acrylate), poly(butyl(meth)acrylate),poly(isobutyl(meth)acrylate), poly(hexyl(meth)acrylate),poly(isodecyl(meth)acrylate), poly(lauryl(meth)acrylate),poly(phenyl(meth)acrylate), poly(methyl acrylate), poly(isopropylacrylate), poly(isobutyl acrylate), poly(octadecyl acrylate)(polyacrylic acids), and copolymers and mixtures thereof, polydioxanoneand its copolymers, polyhydroxyalkanoates, polypropylene fumarate),polyoxymethylene, poloxamers, poly(ortho)esters, poly(butyric acid),poly(valeric acid), poly(lactide-co-caprolactone), trimethylenecarbonate, polyvinylpyrrolidone, polyorthoesters, polyphosphazenes, andpolyphosphoesters, and blends and/or block copolymers of two or moresuch polymers.
 47. A pharmaceutical composition comprising a polymericbead or particle, an antibody according to any one of claims 18 to 37,and/or an antigen presenting complex of any one of claims 38 to
 46. 48.The pharmaceutical composition of claim 47, comprising polymericPLGA-PEG particles, which are optionally PLGA-PEG-maleimide particles,having a size in the range of about 100 to 200 nm.
 49. Thepharmaceutical composition of claim 47 or 48, wherein the particles havea surface charge of about −0 to −15 mV, and optionally a surface chargeof about −5 to about −15 mV.
 50. The pharmaceutical composition of anyone of claims 47 to 49, comprising about 100 to 1500 protein ligands perparticle, the protein ligands each coupled through asulfhydryl-maleimide chemistry.
 51. The pharmaceutical composition ofany one of claims 47 to 50, further comprising a pharmaceuticallyacceptable carrier for intravenous, intra-arterial, subcutaneous,intradermal, intralymphatic, or intra-tumoral administration.
 52. Thepharmaceutical composition of any one of claims 47 to 51, wherein theparticles are substantially spherical or about spherical.
 53. Thepharmaceutical composition of any one of claims 47 to 52, wherein thePLGA is a polymer of about 50% lactic acid (LA) and 50% glycolic acid(GA).
 54. The pharmaceutical composition of any one of claims 47 to 53,wherein the PLGA polymer has a molecular weight of from about 25K toabout 35K, and the PEG has a molecular weight of from about 3K to about10K.
 55. The pharmaceutical composition of any one of claims 47 to 54,having from 400 to 1000 ligands per particle.
 56. The pharmaceuticalcomposition of any one of claims 47 to 55, wherein the anti-CD28 ligandis an antigen-binding antibody fragment.
 57. The pharmaceuticalcomposition of any one of claims 47 to 56, wherein the anti-CD28 ligandcomprises a scFv.
 58. The pharmaceutical composition of any one ofclaims 47 to 57, wherein the HLA ligand is dimeric.
 59. Thepharmaceutical composition of claim 58, wherein the HLA is HLA-A*02:01.60. The pharmaceutical composition of claim 58 or 59, wherein the HLAcomprises an immunoglobulin heavy chain fusion, and optionally does notcomprise an immunoglobulin light chain.
 61. The pharmaceuticalcomposition of any one of claims 47 to 60, further comprising anantigenic peptide for presentation to T cells.
 62. The pharmaceuticalcomposition of claim 61, wherein the pharmaceutical composition isco-formulated with an antigenic peptide for presentation to T cells. 63.The pharmaceutical composition of claim 61 or 62, wherein the antigenicpeptide is one or more of tyrosinase, MAGE-A1, MAGE-A3, gp100, MelanA/Mart-1, gp75/brown, BAGE, NY-ESO-1, and S-100.
 64. The pharmaceuticalcomposition of any one of claims 47 to 63, wherein the pharmaceuticalcomposition is shelf stable.
 65. The pharmaceutical composition of claim64, wherein the pharmaceutical composition is lyophilized.
 66. Thepharmaceutical composition of any one of claims 47 to 65, wherein thecomposition is formulated for parenteral delivery.
 67. A method forinducing the formation of antigen-specific cytotoxic T cells, comprisingadministering a composition of any one of claims 47 to 66 to a patient.68. The method of claim 67, wherein the patient is a cancer patient. 69.The method of claim 67 or 68, wherein the patient is undergoing or hasundergone therapy with one or more checkpoint inhibitors.